1. Field of the Invention
Identification of genes that are differentially expressed in hypoxia and use of the genes and gene products for diagnosis and therapeutic intervention.
2. Description of Related Art
The level of tissue oxygenation plays an important role in normal development as well as in pathologic processes such as ischemia. Tissue oxygenation plays a significant regulatory role in both apoptosis and in angiogenesis (Bouck et al, 1996; Bunn et al, 1996; Dor et al, 1997; Carmeliet et al, 1998). Apoptosis (see Duke et al, 1996 for review) and growth arrest occur when cell growth and viability are reduced due to oxygen deprivation (hypoxia). Angiogenesis (i.e. blood vessel growth, vascularization), is stimulated when hypooxygenated cells secrete factors which stimulate proliferation and migration of endothelial cells in an attempt to restore oxygen homeostasis (for review see Hanahan et al, 1996).
Ischemic disease pathologies involve a decrease in the blood supply to a bodily organ, tissue or body part generally caused by constriction or obstruction of the blood vessels as for example retinopathy, acute renal failure, myocardial infarction and stroke. Therefore apoptosis and angiogenesis as induced by the ischemic condition are also involved in these disease states. Neoangiogenesis is seen in some forms of retinopathy and in tumor growth. It is recognized that angiogenesis is necessary for tumor growth and that retardation of angiogenesis would be a useful tool in controlling malignancy and retinopathies. Further, it would be useful to induce tumorigenic cells to undergo apoptosis (i.e. programmed cell death).
However, these processes are complex cascades of events controlled by many different genes reacting to the various stresses such as hypoxia. Expression of different genes reacting to the hypoxic stress can trigger not only apoptosis or angiogenesis but both. In cancer it has been observed that apoptosis and angiogenesis related genes are therapeutic targets. However, hypoxia itself plays a critical role in the selection of mutations that contribute to more severe tumorigenic phenotypes (Graeber et al., 1996). Therefore identifying candidate genes and gene products that can be utilized therapeutically not only in cancer and ischemia and that may either induce apoptosis or angiogenesis or to retard the processes is needed. It would be useful to identify genes that have direct causal relationships between a disease and its related pathologies and an up- or down-regulator (responder) gene.